Svelte 5: Add ability to manually specify dependencies for `$effect` rune

[kyoshino]

Describe the problem

Dependencies are always unclear in Svelte, and Svelte 5 has causes some new infinite loops as mentioned in #13192. See also #12908.

Describe the proposed solution

Just like useEffect in React, I would like to use the optional second argument of the $effect rune to specify dependencies and untrack other states:

$effect(() => {
  // your logic
}, [a, b, c]);

Basically this is a shorthand of:

$effect(() => {
  void a;
  void b;
  void c;
  untrack(() => {
    // your logic
  });
});

(I usually use void to explicitly specify dependencies)

Importance

would make my life easier

[dummdidumm]

Closing as duplicate of #9248

[takeseem]

I'm a svelte v5 a new developer.

$effect is very power. but ... dep is hell

• my resolve：

import { untrack } from 'svelte';

export function useEffect(fn: () => void, ...deps: any[]) {
	untrack(fn);
}

• useEffect work

  $effect(() => {
    useEffect(() => {
      if (!changed) reset();
    }, user);
  });